1. Field of the Invention
The present invention relates to a flow rate measuring apparatus for measuring, for example, the intake air mass of an internal combustion engine.
2. Description of the Related Art
A flow rate measuring apparatus for measuring the intake air flow rate is widely used in an electronically-controlled fuel injection system for an engine of a car or the like. In an environment in which the ambient temperature of the flow rate measuring apparatus varies, the output error of the flow rate measuring apparatus needs to be reduced even when the ambient temperature varies.
For a conventional flow rate measuring apparatus, a technique has been disclosed that uses as a detection circuit a bridge circuit including a heat generating resistor, a temperature measuring resistor, a fixed resistor and the like to reduce the output error due to variation in ambient temperature (temperature characteristic error) by appropriately selecting the fixed resistor (for example, see Patent Document 1).
[Patent Document 1] Japanese Patent No. 4,089,152
The conventional flow rate measuring apparatus described in the Patent Document 1 cannot accurately correct the temperature characteristic error due to variation in ambient temperature in response to the flow rate and temperature of intake air, with an inadequate reduction in the temperature characteristic error.